Consolidated Statement of Shareholders' Equity and Comprehensive Income (USD $)	Total	Common Stock [Member]	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Loss	Comprehensive Income
Beginning Balance at Dec. 31, 2010	$ 473,311,000	$ 82,000	$ 102,620,000	$ 379,826,000	$ (9,217,000)
Beginning Balance, Shares at Dec. 31, 2010	41,065,000	41,065,000
Issuance of common stock under stock option plans	27,837,000	3,000	27,834,000
Issuance of common stock under stock option plans, Shares	1,351,000	1,347,000
Stock-based compensation expense	5,829,000		5,829,000
Excess tax benefit from stock option exercises	3,624,000		3,624,000
Reduction of tax benefit for research and development credits as a result of stock option accounting	(63,000)		(63,000)
Repurchase of common stock	(10,000,000)	(1,000)	(9,999,000)
Repurchase of common stock, Shares		(337,000)
Payment of dividends	(10,897,000)			(10,897,000)
Comprehensive income:
Net income	50,770,000			50,770,000		50,770,000
Net unrealized gain on available-for-sale investments, net of tax of $62	48,000				48,000	48,000
Foreign currency translation adjustment, net of tax of $26	902,000				902,000	902,000
Comprehensive income						51,720,000
Ending Balance (unaudited) at Oct. 02, 2011	$ 541,361,000	$ 84,000	$ 129,845,000	$ 419,699,000	$ (8,267,000)	$ 51,720,000
Ending Balance, Shares (unaudited) at Oct. 02, 2011	42,075,000	42,075,000